Advancing age is accompanied by several alterations in sleep-wake behavior including nocturnal sleep disruption and an increase in daytime sleep tendency. Age is also associated with a number of medical disorders that can impact sleep quality. Population-based data show that sleep-disordered breathing (SDB), a chronic condition that is characterized by profound alterations in sleep structure, is also common in middle- aged and older adults. Although the biology of sleep has been a topic of intense research, the distinct effects of age versus age-associated illness on sleep structure have not been adequately addressed. The overall objective of this application is to delineate the distinct effects of age and SDB on sleep structure and determine whether the alterations in sleep structure predict cardiovascular and non-cardiovascular endpoints, specifically daytime sleepiness and quality of life, across the adult life span. Novel analytical methods that draw upon the expertise of various scientific disciplines are proposed to analyze the electroencephalographic data collected during sleep to: (1) characterize the independent effects of age and SDB on sleep structure;and (2) determine the role of sleep structure as a putative intermediate in the causal pathway toward cardiovascular and non-cardiovascular outcomes. The current application will utilize data collected by the Sleep Heart Health Study, a multi-center longitudinal study on the cardiovascular consequences of SDB. The investigative team, which spans multiple disciplines including epidemiology, biostatistics, sleep medicine, and the engineering sciences, brings the necessary expertise to examine trajectories of sleep structure with healthy aging and age-associated illnesses. The significance of this application is that it will make a valuable contribution by providing a better understanding of the mechanistic role of sleep in increasing the age-related vulnerability to various conditions that impact general health. Insight will also be gained into the degree to which other conditions such as cardiovascular and pulmonary disease impact sleep. Although basic 'mechanistic'links cannot be directly addressed, questions related to which aspects of sleep (e.g., EEC activity, recurrent sleep-stage shift) best discriminate clinical outcomes. Finally, we expect to also provide new and much needed information on how factors such as gender and race influence sleep and quantify the adverse sleep-related effects of behaviors such alcohol use, cigarette smoking, and caffeine consumption.